JPH0637313A - Thin-film semiconductor device and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a semiconductor device in which an N-type TFT for a picture element part and an N-type TFT and a P-type TFT of a complementary (C) type circuit for driving the former are built in the same substrate, and also to provide the manufacture thereof without increasing the number of a photo-resist process more than that in a conventional N-type circuit. CONSTITUTION:A gate electrode 2, a gate insulating film 3 and silicon layers (5, 4 & 5) for each TFT are sequentially formed on a transparent substrate 1, and after N-type impurities are doped thereinto, photo etching is applied for the division of the substrate into first through third islands to make a semiconductor layer for each TFT so that the first island is formed to act as an N-type semiconductor layer 6 for a picture element part and the second island is formed to act as an N-type semiconductor layer 6 for a C-type circuit, and then a film of ITO for a picture element electrode 8 is so accumulated as to cover only the first and the second islands. After that, doping is performed in such a manner that the concentration of P-type impurities becomes higher than that of N-type impurities to form the third island in a P-type semiconductor layer for the C-type circuit, and then the source/drain electrodes 9 for each TFT and also a protective film 10 are formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film semiconductor device,
In particular, the present invention relates to a thin film transistor used in a liquid crystal display device and a manufacturing method thereof.

[0002]

2. Description of the Related Art As a thin film transistor (TFT) used in a liquid crystal display device, for example, an amorphous silicon (a-Si) TFT or a polycrystalline silicon (p-Si) TFT is formed on an insulating substrate such as glass. For example, in an active matrix driving liquid crystal display (LCD), these a-Si TFTs and p-Si TFTs are used as semiconductor elements (pixel TFTs) in an image display area that drives liquid crystals.

In addition to the pixel TFT, a driving circuit for driving the pixel TFT is built on the same substrate by using these a-Si TFT and p-Si TFT, and as a result, the price of the display device and the number of connecting lines to the outside are reduced. Attempts have been made to reduce it. The drive circuit (built-in drive circuit) formed on the substrate is
The following two methods are used.

In the first method, the channel semiconductor layer of the TFT is a layer in which impurities are not added with particular consideration, and the channel semiconductor layer is a contact region with source / drain electrode terminals for taking out current from the channel semiconductor layer. A circuit type (N-channel type TFT, in which phosphorus or antimony is added to form an N-type semiconductor layer).
Type circuit).

In the second method, one of the TFTs is an N-channel type as described above, and the other TFT is a P-channel with impurities such as boron added to the contact region between the channel semiconductor layer and the source / drain electrode terminals. As a type, there is a circuit type (C type circuit) configured by two types of complementary TFTs of these N channel type and P channel type. These N-type circuits, C
Type circuits are NMs in the field of integrated circuits (ICs).
Although called an OS or CMOS circuit, an oxide film may not be used as a gate insulating film in the field of TFTs, so the names of N-type circuit and C-type circuit are used below.

Needless to say, the C-type circuit is superior to the N-type circuit in terms of circuit performance, and exhibits high-speed response and low power consumption characteristics. However, there is a drawback that the number of manufacturing steps is significantly increased to form a C-type circuit. This occurs due to the step of forming the C-type circuit TFT. In the order of steps, when adding (doping) N-type impurities to the channel semiconductor layer, the semiconductor layer to be a P-channel TFT is Impurities are
This is because, for example, a step of protecting the N-channel TFT with a photoresist is required in order to prevent ping, for example, a step of protecting the N-channel TFT with a photoresist is required when doping P-type impurities.

As an example of a method of manufacturing a thin film semiconductor device for forming a built-in driving circuit of a liquid crystal display device by a C-type circuit,
1985 Conference Record of International Display Resea
rch Conference) Section 9.

[0008]

In the above-mentioned prior art, in order to realize a high-performance C-type built-in circuit, the number of manufacturing steps increases significantly, resulting in an increase in the cost of the liquid crystal display device. was there.

An object of the present invention is to maintain the high performance of the C-type circuit and to increase the number of photoresist steps in the process of forming a thin film semiconductor device for the C-type circuit, and to increase the N-type of the image area. It is an object of the present invention to provide a thin film semiconductor device having a structure in which a peripheral circuit which is a C type circuit for driving the N type circuit together with the circuit can be built in on the same substrate, and a manufacturing method thereof.

[0010]

To achieve the above object, a thin film semiconductor device of the present invention comprises a first gate electrode, a gate insulating film, a first N-type semiconductor layer, which are sequentially formed on a substrate, An N-type thin film transistor of a pixel portion composed of a pixel electrode, a first source / drain electrode and a protective film; a second gate electrode, a gate insulating film, and a second N-type semiconductor layer sequentially formed on the substrate An N-type thin film transistor which is composed of a second source / drain electrode and a protective film and serves as one of complementary driving circuits for driving the N-type thin film transistor of the pixel portion; and a third gate sequentially formed on the substrate. And a P-type thin film transistor which is composed of an electrode, a gate insulating film, a P-type semiconductor layer, a third source / drain electrode, and a protective film and serves as the other of the complementary driving circuit parts. , A second source / drain electrode is characterized by comprising a thin film formed of a material for the pixel electrode as the lower layer.

A method of manufacturing a thin film semiconductor device according to the present invention is the above method of manufacturing a thin film semiconductor device, in which impurities are not contained on a gate insulating film formed to cover the first to third gate electrodes. Deposit an amorphous silicon film,
The portion of the amorphous silicon film on the second and third gate electrodes is polycrystallized, the amorphous silicon film is further deposited, and the N-type impurities are doped. Then, the amorphous silicon film is applied on the first to third gate electrodes. The silicon film portions are each photolithographically divided into first to third islands, and thus the first islands are formed as the first N-type semiconductor layer and the second islands are formed as the second N-type semiconductor layer. Then, a transparent pixel electrode film made of indium tin oxide is deposited so as to cover only the first and second islands,
After that, P-type impurities are doped at a higher concentration than the N-type impurities to form the third islands as P-type semiconductor layers, and then the first to third source / drain electrode films are deposited. Further, of the semiconductor layer between the source / drain, the impurity semiconductor layer on the surface is removed by etching using the source / drain electrode as a mask, and finally a protective film is formed. As a result, the indium tin oxide, which is the material for the pixel electrode, forms the pixel electrode in the N-type thin film transistor of the pixel portion, and at the same time, forms one of the second source / drain electrodes in the N-type thin film transistor which is one of the complementary driving circuits. A lower layer to be a part will be formed.

[0012]

According to the method of manufacturing a thin film semiconductor device of the present invention,
To form a P-type semiconductor layer of a P-type thin film transistor of a complementary driving circuit unit by doping P-type impurities,
Before that, the N-type semiconductor layer of one N-type thin film transistor of the complementary drive circuit section is masked with the pixel electrode material at the same time when the pixel electrode of the N-type thin film transistor of the pixel section is formed. The number of photoresist processes for masking the N-type semiconductor layer of the N-type thin film transistor is not increased.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view for explaining the structure of the thin film semiconductor device of the first embodiment of the present invention. This thin film semiconductor device is a liquid crystal display (L
Pixel TFT (TF shown on the left in the figure)
T) and the peripheral circuit TFT that drives the pixel TFT (in the figure,
Center and two TFTs shown on the right). The peripheral circuit is composed of an N-type TFT and a P-type TFT, and the pixel T
It is built in on the same substrate as the FT.

In FIG. 1, 1 is a transparent insulating substrate and 2 is a transparent insulating substrate.
Is a gate electrode, 3 is a gate insulating film, 4 is a polycrystalline silicon layer not doped with impurities, 5 is an amorphous silicon layer not doped with impurities, and 6 is doped with impurities such as phosphorus. N + layer, 7 is a p + layer doped with impurities such as boron, and 8 is indium tin oxide (I
TO is a pixel electrode, 9 is a source / drain wiring electrode made of Cr or the like, and 10 is a TFT protective film.

The thin film semiconductor device of this embodiment realizes a visual display terminal (VDT) with a diagonal of 10 inches in the display section. In this case, the number of pixels in the display portion is 480 × 640 × (3), the pixel TFT used in the display portion is an N-type TFT having an inverted stagger structure, while the TFT used in the built-in peripheral circuit is an N-type TFT. And P-type TFT.

Next, a process of forming the pixel TFT of the display portion and the N-type TFT and P-type TFT of the built-in peripheral circuit will be described. First, (1) a Cr film, which is the gate electrode 2, is deposited on the glass substrate 1 by a sputtering method at a rate of 3000 liters. (2)
After patterning the gate electrode 2, a SiN film, which is the gate insulating film 3, is deposited by 3000 Å by plasma CVD method. (3) Next, an a-Si film with no added impurities is deposited. (4) Here, an N-type TFT that becomes a peripheral circuit
And, the excimer laser is irradiated with 200 mJ / cm ² only on the portion where the P-type TFT is formed and the a-Si film is exposed to p-S.
Convert to i-layer 4. (5) Next, the a-Si film 5 to which impurities are not intentionally added is 2,000 by the plasma CVD method.
Å Accumulate. A two-layer structure of p-Si / a-Si is obtained in the peripheral circuit portion, and a single-layer structure of a-Si is obtained in the pixel portion. (6) Next, phosphorus is doped by a doping method such as an ion implantation method to remove 3 from the surface of the a-Si layer 5.
An n + semiconductor layer 6 is formed to a depth of about 00Å.
(7) S on the gate insulating film 3 by the photo-etching process
The i layer is divided into islands to form an island in the peripheral circuit portion and an island in the pixel portion. (8) After that, transparent indium tin oxide (ITO), which is the pixel electrode 8, is deposited by the sputtering method and patterned by a photoetching process.

Step of Depositing Pixel Electrode 8 The following procedure is important in the manufacturing method of the present invention, so that FIG.
This will be described in detail with reference to FIG.

The pixel electrode 8 is n only for the N-type TFT in the peripheral circuit portion shown in FIG. 2 and the TFT in the pixel portion (FIG. 1).
+ Is deposited so as to be in contact with the semiconductor layer 6, and is used as a mask for the N-type TFT in the peripheral circuit portion and in the pixel portion.
Is formed as a pixel electrode. (9) After that, boron is doped by a doping method such as an ion implantation method to form the p + semiconductor layer 7 at a depth of about 400 Å from the surface of the a-Si layer 5. At this time, if the impurity concentration of boron to be implanted is set to be an order of magnitude higher than the impurity concentration of phosphorus,
The Si islands that become N-type TFTs are doped with the pixel electrode 8 as a mask, so that a partial gap is converted into a p + layer. On the other hand, since the pixel electrode is not formed on the Si island which becomes the P-type TFT, the entire surface of the Si island is converted into the p + layer over a depth of 400Å. (10)
Then, as shown in FIG.
Cr to be the drain wiring electrode 9 is deposited and patterned by a photoetching process, and as shown in FIG. 4, dry etching of each Si island is performed at 600 Å. Here, with respect to the Si island which becomes the P-type TFT, Cr which becomes the drain wiring electrode 9 is formed so as to be in contact with the n + semiconductor layer 6, and the p + layer on the Si surface between the source / drain is removed. It becomes possible to operate. (11) Finally, when a passivation film is formed, a TFT having an inverted stagger structure is completed.

When a liquid crystal is sealed between the thin film semiconductor device constructed as described above and another semiconductor device having a polarizing plate, a color filter and a transparent electrode formed on another glass substrate, 10 inches is obtained. The size VDT display device is completed.

FIG. 5 shows the overall structure of a liquid crystal display device using the thin film semiconductor device manufactured as described above. This liquid crystal display device is composed of a TFT liquid crystal display unit 50, a scanning circuit 51, a switch matrix circuit 52 serving as a time function converting means, and a signal side circuit 53.
A scanning signal is sent from the scanning circuit 51 to each liquid crystal element of the liquid crystal display unit 50 through the scanning lines 71 to 73, and a signal circuit 53 passes through the switch matrix circuit 52 and signal lines 74 to 76. A signal is sent. With the above configuration,
The N-type TFT having the ITO film according to the present invention is used for the switch 60a in the liquid crystal display unit 50 and the switches 61 to 63 in the switch matrix circuit 52. The switch in the scanning circuit 51 is an ITO according to the present invention.
It is composed of a C-type circuit (shown in FIG. 4) configured by combining an N-type TFT having a film and a P-type TFT.

Next, the operation of the apparatus shown in FIG. 5 will be briefly described. The scanning circuit 51 uses 2 as a timing signal.
The CKV signal of the phase clock and the input voltage Vin are input. On the other hand, the signal side circuit 53 receives the digital data signal data which determines the display state of the liquid crystal, outputs it as the color signal voltages Vs1 to Vsm, and distributes it to each of the signal lines 74 to 76 as a matrix switch.

Next, the circuit configuration of the scanning circuit 51 will be described with reference to FIG. FIG. 6 shows one of the scan lines 71 to 73.
A scanning circuit corresponding to the main portion is shown, and this scanning circuit is composed of a shift register and a buffer circuit for amplifying a voltage as a function. In the figure, the switch 80 is an N-type TF
At T, the switch 81 is composed of a P-type TFT.
Next, the operation of the scanning circuit will be described. 2 shift registers
Timing is taken by the phase clocks (Vc1, Vc2) and the respective inversion clocks (Vcn1, Vcn2), the input voltage Vin is inverted (shifted) and transferred to the buffer, and at the same time, this is the input voltage of the shift register corresponding to the next scanning line. Becomes The buffer is amplified in the same phase as the inverted voltage and outputs a pulse voltage having a maximum voltage of Vdd2, which becomes the scanning voltage Vg of the liquid crystal display unit. Here, Vdd1 and Vdd2 are DC voltages.

The shift register of the C-type circuit formed by using the thin film semiconductor device of the present invention has an operating frequency of its voltage which is 20 times faster than that of the conventional N-type circuit, and consumes three orders of magnitude less power. Characterized.

Next, a second embodiment of the present invention is shown in FIG. In this embodiment, the gate electrode 2 is sequentially formed on the insulating substrate 1.
The process up to the step of forming the p-Si layer by the gate insulating film 3, the first-layer a-Si film and the laser anneal is the same as the method of forming the thin film semiconductor device of the first embodiment. After that, the insulating film 22 made of SiN is deposited on the p-Si layer, and photoetching is performed to mask the central portion of the p-Si layer. Next, phosphorus is doped by a doping method such as an ion implantation method to form an n + semiconductor layer 6 on the p-Si layer 4 not masked by the insulating film 22.

After that, transparent ITO which is the pixel electrode 8 is deposited by a sputtering method, and patterned by a photoetching process.
To learn. The pixel electrode 8 is an N-type T of the peripheral circuit portion.
Only the FT and the TFT of the pixel portion are formed so as to be in contact with the n + semiconductor layer 6, and N of the peripheral circuit portion is formed.
It is formed as a mask for the TFT of the mold and as a pixel electrode for the TFT of the pixel portion. Next, boron is doped by a doping method such as an ion implantation method to form the p + semiconductor layer 7 on the p-Si layer 4. At this time, if the impurity concentration of the implanted boron is set to be an order of magnitude higher than the impurity concentration of phosphorus, the insulating film 2 will be removed from the Si islands that will become N-type TFTs.
2. Since the pixel electrode 8 is used as a mask, the p + layer is not formed. On the other hand, with respect to the p-Si island which becomes the P-type TFT, since the mask of the pixel electrode is not formed, the n + layer is converted into the p + layer. Next, the source /
Cr serving as the drain wiring electrode 9 is deposited and patterned by a photoetching process to enable TFT operation. After that, a passivation film is formed to complete a TFT having an inverted stagger structure.

In this embodiment, the number of masks for the photo-etching process of the insulating film 22 is increased by one, but the thickness of the Si layer can be reduced to about 1/10 as compared with the TFT in the first embodiment, and An increase in leak current during irradiation can be reduced.

[0027]

According to the present invention, an N-type thin film transistor of a pixel portion and an N-type thin film transistor and a P-type thin film transistor forming a complementary driving circuit for driving the N-type thin film transistor of the pixel portion are provided on the same substrate. In the manufacturing method of the thin film semiconductor device, before the P type semiconductor layer of the P type thin film transistor of the complementary driving circuit is formed by doping the P type impurity, the N of the complementary driving circuit is formed.
The N-type semiconductor layer of the N-type thin film transistor is masked with the electrode material of the N-type thin film transistor of the pixel section at the same time as forming the pixel electrode of the N-type thin film transistor. Therefore, a photoresist for masking the N-type semiconductor layer of the N-type thin film transistor of the complementary driving circuit. There is an effect that a complementary driving circuit that operates at high speed and consumes less power can be manufactured without increasing the number of steps. Finally, there is an effect that the peripheral drive circuit can be built in the liquid crystal display substrate or the image processing apparatus.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an inverted stagger structure TFT according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view (No. 1) of the TFT in the manufacturing process of the inverted stagger structure TFT.

FIG. 3 is a cross-sectional view (No. 2) of the TFT in the manufacturing process of the inverted stagger structure TFT.

FIG. 4 is a cross-sectional view (No. 3) of the TFT in the manufacturing process of the inverted stagger structure TFT.

FIG. 5 is an overall configuration diagram of a TFT liquid crystal panel.

FIG. 6 is an equivalent circuit diagram of a scanning circuit in a TFT liquid crystal panel.

FIG. 7 is a sectional view of a TFT showing a second embodiment of the present invention.

[Explanation of symbols]

 1 Insulating Substrate 2 Gate Electrode 3 Gate Insulating Film 4 Polycrystalline Silicon 5 Amorphous Silicon 6 n + Semiconductor Layer 7 p + Semiconductor Layer 8 Pixel Electrode (ITO) 9 Source / Drain Wiring Electrode 10 Protective Film 22 Insulating Film 50 TFT Liquid crystal display unit 51 Scanning circuit 52 Switch matrix circuit 53 Signal side circuit 60a Switch (N-type TFT) 61-63 switch (N-type TFT) 80 Switch (N-type TFT) 81 Switch (P-type TFT)

Claims (5)

[Claims] 1. A pixel portion including a first gate electrode, a gate insulating film, a first N-type semiconductor layer, a pixel electrode, a first source / drain electrode, and a protective film, which are sequentially formed on a substrate. An N-type thin film transistor; a second gate electrode, a gate insulating film, a second N-type semiconductor layer, a second source / drain electrode and a protective film, which are sequentially formed on the substrate, -Type thin film transistor which is one of complementary driving circuits for driving the thin-film transistor, and a third gate electrode, a gate insulating film, a P-type semiconductor layer, a third source / drain electrode and a protective film which are sequentially formed on the substrate. P, which is the other of the complementary driving circuits.
Thin film semiconductor device having a thin film transistor, wherein the second source / drain electrode includes a thin film formed of the pixel electrode material as a lower layer. 2. The first N-type semiconductor layer is formed of amorphous silicon, the contact region with the pixel electrode is an N-type conductor, and the second N-type semiconductor layer is in contact with the gate insulating film. The polycrystalline silicon layer is formed of polycrystalline silicon and amorphous silicon in that order, and the contact region with the lower layer that is formed simultaneously with the pixel electrode becomes an N-type conductor, and the P-type semiconductor layer is a polycrystalline silicon layer in order from the side in contact with the gate insulating film. ,
The thin film semiconductor device according to claim 1, wherein the thin film semiconductor device is formed of an amorphous silicon layer, and a contact region with the third source / drain electrode is a P-type conductor. 3. A pixel portion comprising a first gate electrode, a gate insulating film, a first N-type semiconductor layer, a pixel electrode, a first source / drain electrode and a protective film, which are sequentially formed on a substrate. An N-type thin film transistor; a second gate electrode, a gate insulating film, a second N-type semiconductor layer, a second source / drain electrode and a protective film, which are sequentially formed on the substrate, -Type thin film transistor which is one of complementary driving circuits for driving the thin-film transistor, and a third gate electrode, a gate insulating film, a P-type semiconductor layer, a third source / drain electrode and a protective film which are sequentially formed on the substrate. P, which is the other of the complementary driving circuits.
A thin film semiconductor device including: a thin film transistor; forming first to third gate electrodes on a substrate; depositing a gate insulating film; depositing an amorphous silicon film; After polycrystallizing the amorphous silicon film on the portion overlying the gate electrode, further depositing the amorphous silicon film, and doping with N-type impurities, the silicon film portions overlying the first to third gate electrodes are respectively formed into first and second portions. The first to third islands are separated by photo-etching, and thus the first islands are used as the first N-type semiconductor layer and the second islands are used as the second N-type.
Type semiconductor layer, then a film of the pixel electrode is deposited so as to cover only the first and second islands, and then P-type impurities are doped at a higher concentration than the N-type impurities. 3. A method of manufacturing a thin film semiconductor device, wherein the third island is formed as a P-type semiconductor layer, and then the first to third source / drain electrodes and the protective film are sequentially formed. 4. The method of manufacturing a thin film semiconductor device according to claim 3, wherein transparent indium tin oxide is used as the material for the pixel electrode. 5. An image processing apparatus comprising the thin film semiconductor device according to claim 1.